I have tested this myth myself, and it seems true that you are lighter in the day. It makes sense being your muscles are relaxed because you havent used them much yet that day and you also dont have water or food in your system. I like the Weight Watcher scale (which measures in the metric system as well as in pounds) so it's good if you are in the UK. It reads out in digital which i like and you can also store up to 5 measurement in it if you want to track your weigh-ins.